[R] "unfurling" rankings into a matrix of preferences

[Dimitri Liakhovitski]

Wow!

On Mon, Jul 27, 2015 at 5:28 PM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
> ## I leave it to you to add the NA edges
>
>> rk <- c(2,4,3,1)
>
>> outer(rk,rk,"<")+0
>
>      [,1] [,2] [,3] [,4]
> [1,]    0    1    1    0
> [2,]    0    0    0    0
> [3,]    0    1    0    0
> [4,]    1    1    1    0
>
>
>
> Cheers,
> Bert
>
> Bert Gunter
>
> "Data is not information. Information is not knowledge. And knowledge
> is certainly not wisdom."
>    -- Clifford Stoll
>
>
> On Mon, Jul 27, 2015 at 12:38 PM, Dimitri Liakhovitski
> <dimitri.liakhovitski at gmail.com> wrote:
>> I have 5 items in total (1:5), but I show a person only 4 items (1:4)
>> and ask this person to rank items 1:4 in terms of preferences (1 is
>> best, 2 is second best, 4 is worst), and I get a vector of ranks:
>> ranks <- c(2,4,3,1)
>>
>> # That means that this person liked item 4 best and item 2 worst.
>>
>> I would like to "unfirl" this vector of ranks into a matrix of
>> preferences where if the row item prefers the column item, then it's a
>> 1. Otherwise, it's a zero. So, the output should be a 5 by 5 matrix
>> (because overall we have 5 items, not 4, but item 5 did not
>> participate in rankings), and it would always have zeros in a
>> diagonal.:
>>
>> 0    1    1    0 NA
>> 0    0    0    0 NA
>> 0    1    0    0 NA
>> 1    1    1    0 NA
>> NA NA NA NA 0
>>
>> I can loop through all possible pairs the person saw and fill the
>> matrix accordingly, but it seems like a lot of looping. Could one do
>> it in a more elegant way?
>>
>> Thank you very much!
>>
>>
>> --
>> Dimitri Liakhovitski
>>
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-- 
Dimitri Liakhovitski